Proceedings of the 12th International INQUA meeting on paleoseismology, active tectonic and archaeoseismology

124 PATA Days 2024 1 2 T H I N T E R N AT I O N A L I N Q U A M E E T I N G O N PA L E O S E I S M O L O G Y , A C T I V E T E C T O N I C S A N D A R C H A E O S E I S M O L O G Y ( PATA ) , O C T O B E R 6 T H - 1 1 T H , 2 0 2 4 , L O S A N D E S , C H I L E K E Y W O R D S Soft-deformation structures, amazon, magnitude, Ecuador (1) Technical University of Manabí. Master's in Risk Prevention and Management at the Graduate School of the Technical University of Manabí. Portoviejo, Ecuador. (2) Earth and Climate Sciences Research Group. Universidad Regional Amazónica Ikiam. Tena, Ecuador. *Email: ecornejo4965@utm.edu.ec Carolina Cornejo (1,2) Oswaldo Guzmán (2) Corina Campos (2) ANALYSIS OF SOFT-SEDIMENT DEFORMATION STRUCTURES IN THE TENA FORMATION - ORIENTE BASIN OF ECUADOR: PALEOSEISMOLOGIC IMPLICATIONS A B S T R A C T The analysis of soft-sediment deformation structures in the Ecuadorian Amazon, particularly within the Tena Formation, had not been documented until now. This study aims to characterize the deformation mechanisms and triggering events of these soft- deformation structures using coseismic stratigraphy. The findings reveal various ductile deformation structures, including loop bedding, pseudonodules, ball-and-pillow, deformed lamination, load cast, and flame-like structures. The deformation mechanisms of these structures are associated with liquefaction and/or fluidization, likely induced by seismic activity. Ultimately, magnitude interpretation suggests a correlation between these structures and seismic events surpassing a magnitude of 5. Documenting these deformation structures in Cretaceous sedimentary deposits highlights the tectonic activity of that age, which can be related to the onset of basin inversion due to the uplift of the Andes. I N T R O D U C T I O N Soft-SedimentDeformationStructures(SSDS)serveasindicators of both sedimentary and tectonic processes within sedimentary deposits that have not yet lithified. These structures showcase diverse morphologies and have been extensively investigated across various geological ages and depositional environments, encompassing lacustrine, glaciolacustrine, transitional, marine, fluvial, eolian, and paralic settings (Montenat et al., 2007; Moretti & Ronchi, 2011; Shanmugam, 2017). The formation of SSDS can be attributed to different mechanisms, including overloading,